The present invention constitutes an improvement over the fused eyeletting machines disclosed in U.S. Pat. Nos. 3,739,141 and 3,940,590 and in U.S. patent application Ser. No. 583,219 filed Oct. 24, 1984, now U.S. Pat. No. 4,584,460. The disclosures of the above-identified U.S. patents and U.S. patent application are incorporated herein by reference.
U.S. Pat. No. 3,739,141 discloses a fused eyeletting machine having a C-shaped frame, with the upper arm of the frame housing an upper tool, and the lower arm housing a resilient support structure for a lower tool which enables the eyelet setting pressure to be pre-determined. The upper tool is brought into contact with the lower tool by means of a toggle arrangement which is pivoted to the upper arm of the frame.
U.S. Pat. No. 3,940,590 describes an improved version of the machine disclosed in '141 patent. In the machine described in the '590 patent, the upper arm of the C-shaped frame terminates in a pair of spaced-apart tool support members, and a double stop toggle mechanism is mounted between those support members for actuating movement of the upper tool with respect to the lower tool.
The '219 pending U.S. application describes a further improved fused eyeletting machine which utilizes a novel and simplified support structure for resiliently biasing the lower tool to exert a pre-determined force against which the upper tool acts during the eyelet setting operation. As with the machines described in the '141 and '590 U.S. patents, the upper tool is actuated by means of a toggle arrangement.
One of the disadvantages associated with the structures described above arises from the use of a toggle arrangement for actuating movement of one of the tools towards and away from the other tool. In those toggle arrangements, the stroke length is fixed so that difficulties in operation sometimes arise when boards of different thicknesses or eyelets of different lengths are utilized. These difficulties arise especially in the circuit board repair industry where circuit boards and eyelets of various thicknesses and lengths are encountered. In light of this, care must be taken by the machine operator in each eyelet setting operation to achieve the desired eyelet setting and fusing on the board without crushing the board or distorting the eyelets.
A further problem which arises from the use of toggle actuating arrangements is that most toggle mechanisms are manufactured according to low tolerance specifications, so that difficulties are encountered in achieving accurate and repeatable alignment of the upper and lower tools each time the toggle arrangement is used. This, in turn, gives rise to possible distortion of the eyelets as they are pressed into contact with the board prior to fusing, which in turn impairs the quality of the fused eyelet.
It is therefore a primary object of the present invention to provide an improved eyeletting machine capable of use with equal facility on eyelets and funnelets of different sizes and on printed circuit boards of different thicknesses.
It is another object of the present invention to provide an eyeletting machine which utilizes a novel and simplified tool moving arrangement whereby the eyelet setting tools are brought into aligned contact with each other at a pre-determined eyelet setting pressure, which pressure can not be exceeded despite continued operation of the tool moving arrangement after the pre-determined pressure has been reached.